AN Taisce, the Dublin Civic Group and the Irish Georgian Society are expected to appeal to An Bord Pleanala against Dublin Corporation's decision to grant planning permission for the National Gallery's proposed extension into Clare Street.
All three organisations made submissions to the corporation urging that permission be refused for the £13 million scheme, mainly on the grounds that it would require the demolition of an unlisted Georgian house.
"Although not of the highest quality, owing to major intervention over the years, the house (5 South Leinster Street), holds an extremely important place in the streetscape", due to its prominent location on the approach to Merrion Square, the IGS said.
This would leave 6 South Leinster Street - a very important Georgian house next door - "totally isolated" in a row of modern buildings, it warned. "Our dwindling stock of 18th-century buildings cannot be replaced and should not be depleted further".
Because of its pivotal position in the street, the stone-faced front of the gallery would "loom over" the historic streetscape, changing its character for ever, while the "attention-seeking" projection at first-floor level would be "aggressively" intrusive.
The IGS also objects to a proposed tower, over loo feet high, which is also part of the design. This would be seen as a "featureless extension at variance with the picturesque composition of the existing National Gallery, Leinster House and their surroundings".
An Taisce's submission noted that 5 South Leinster Street had been the home of Lord Kilwarden, "by the standards of the time a relatively liberal Lord Chief Justice", who was assassinated in 1803 during the abortive rebellion led by Robert Emmet.
It also said the house contains some fine 18th-century plaster-work as well as a ballroom at the rear, added in the early 19th century by Archibold Hamilton Rowan, who had been involved in the 1798 Rising as a member of the United Irishmen.
The National Gallery's proposed extension was designed by the British architects, Benson and Forsyth, following a limited international competition. The brief given assumed that 5 South Leinster Street would be demolished.
Dublin Corporation decided to grant permission on the basis that the proposed development was of "national and metropolitan importance". On balance, therefore, it felt that the retention of the house in its "debased condition could not be insisted upon".
